Cleaning Up Sites Contaminated with Radioactive Materials International Workshop Proceedings (2009) / Chapter Skim
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15 Remediation of Contaminated Facilities at the Kurchatov Institute--V. G. Volkov, Yu. A. Zverkov, S. G. Semenov, A. V. Chesnokov, and A. D. Shisha
15 Remediation of Contaminated Facilities at the Kurchatov Institute--V. G. Volkov, Yu. A. Zverkov, S. G. Semenov, A. V. Chesnokov, and A. D. Shisha
Pages 99-109
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From page 99... ...
D Shisha, Russian Research Center -- Kurchatov Institute INTRODUCTION During many years of research activities to develop nuclear technologies for military and civil applications, the Russian Research Center -- Kurchatov Institute accumulated at its site considerable amounts of solid radioactive waste and spent nuclear fuel. Solid radioactive waste produced before the mid-1960s, some of it having high specific activity, had been placed in interim storage at a special site within the Kurchatov Institute.
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From page 100... ...
Available data on the geological structure of the soil, permeability coefficients of subsurface horizons, groundwater level, and volume of radioactivity served as a basis for calculation of the groundwater flow structure and strontium90 dispersal range. Apparently due to a sharp increase in the groundwater level in the early 1990s, the groundwater flow structure changed, resulting in a risk of contamination beyond the Kurchatov Institute. In addition, according to a model created to predict strontium-90 dispersion, if remediation work is done on the temporary radioactive waste sites, the area of groundwater contamination with strontium-90 content exceeding the action level (5 Bq/L)
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From page 101... ...
In the meantime, to evaluate the efficiency of such countermeasures, specialists from the Radon enterprise performed laboratory studies on conditions that would permit efficient chemical reactions involved in underground leaching. The studies were performed using near-bottom soils from Temporary Storage Facility No. 3 (the contaminated area was 10 × 8 m2 and 3 m thick)
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From page 102... ...
TABLE 15-1 Reference Levels of Technogenic Background and Soil Contamination at the Radioactive Waste Disposal Site Monitored Parameter Value Note Equivalent technogenic gamma 2.5 µSv/hr Mean integral dose at Kurchatov Institute background dose rate at the (250 µrem/hr) perimeter: 0.8 mSv/yr (in 2005)
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From page 103... ...
Equivalent gamma dose rates were measured along the depth of the boreholes using a certified UIM-2-2 instrument with a BDMG-100 detector. Collimated detectors were used to measure distribution of specific activities of gamma-emitting radionuclides.
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From page 104... ...
To warn personnel about radiation hazards, working areas were equipped with threshold collimated detectors that produced audible and light alarms when the allowed gamma dose rate level was exceeded. The concrete matrix of the facility was gradually destroyed through the opening in the radiation shielding by an excavator with a hydraulic hammer located on the shielding roof.
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From page 105... ...
4, the radiation situation in working areas and at the entire disposal site was monitored with two gamma locators that measured the ionizing radiation photon flux, taking into account its spectral characteristics. One of the gamma locators was used for continuous monitoring of changes Volkov, V
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From page 106... ...
In addition to monitoring the overall radiation situation, site managers also monitored groundwater activity using a network of observation boreholes located at the radioactive waste disposal site and in the adjoining area. APPLICATION OF DUST-SUPPRESSION TECHNOLOGIES To ensure radiation safety for personnel involved in the work and prevent formation and transfer of radioactive aerosols, all operations involving radioactive waste extraction and disposition of the old storage facilities were performed using dust-suppression technologies.
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From page 107... ...
According to the results of preliminary studies performed by the Bochvar Institute, more than 80 percent of radionuclides in the contaminated soil are accumulated in fine sludge or clay fractions or both. Therefore, the technology of wet decontamination of soil consisting of water-gravity separation and classification of the contaminated soil into size fractions followed by segregation and removal of the fine fraction was adopted for soil decontamination.
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From page 108... ...
About 250 metric tons of metal radioactive waste was decontaminated using the hydroabrasive equipment and then shipped to the Ecomet-S enterprise for remelting. MAIN RESULTS OF THE WORK All 10 old radioactive waste repositories subject to remediation at the waste disposal site have been decommissioned and eliminated.
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From page 109... ...
The volume of activity in the air at the disposal site and within the overall Kurchatov Institute site was by three to five orders of magnitude less than allowable levels for urban populations. External radiation exposure of personnel by years is presented in Table 15-2.
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